
Source: Wikimedia Commons
Harlequin rasbora
A beautiful small fish with orange body and black triangle mark. Schooling looks best in planted tanks.
The harlequin rasbora (Trigonostigma heteromorpha) is a small cyprinid native to slow-moving, blackwater streams and swamps of the Malay Peninsula, Thailand, Sumatra, and Borneo. At 3–4 cm, its copper-orange to pinkish body with a distinctive bold black triangular patch covering the rear half creates an immediately recognizable profile — giving rise to its alternative name, the 'black wedge rasbora.' Introduced to the aquarium hobby in the early 1900s, it achieved iconic status when featured on the cover of William T. Innes' landmark 1935 book 'Exotic Aquarium Fishes.' Soft, slightly acidic water (pH 5.5–7.0) at 24–28°C is ideal; blackwater setups with tannins enhance coloration. Peaceful and schooling, a group of ten or more produces a cohesive, beautiful display. Compatible with virtually all small community fish. Omnivorous and accepts quality granules, flake food, and frozen daphnia. Breeding occurs on the undersides of broad-leafed plants such as Anubias in soft, acidic conditions. A true classic of the freshwater aquarium, beloved consistently across more than a century of the hobby.
Source: Wikipedia (CC BY-SA 4.0)
Origin
streams and swamps of the Malay Peninsula, Thailand, Sumatra, and Borneo
Lifespan
3-5 years
Size
3-4cm
Temperature
22〜28℃
Pellets, Frozen food
Sources: FishBase / Seriously Fish
Edited & verified by: br-choku editorial team
The taxonomic, regulatory, and husbandry data on this page are compiled and verified against the authoritative primary sources below.
Trigonostigma heteromorpha は CITES 非該当。
Sources: Seriously Fish / CITES Appendices (Checklist)
Regulations may change. Always verify the latest information with the relevant authorities.
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Slightly acidic to neutral (pH 5.5-7.0)
Maintain 24-28°C
Schooling of 10+ is beautiful
Perfect compatibility with planted tanks
Beginner. This is a beginner-friendly species. No special equipment or experience is required, and it can be kept successfully with basic care setup.
The ideal temperature for Harlequin Rasbora is 22〜28℃. Avoid sudden temperature changes and maintain a stable environment.
The average lifespan of Harlequin Rasbora is 3-5 years. With proper care and nutrition, they can live a long and healthy life.
Harlequin Rasbora typically reaches 3-4cm as an adult. Size may vary depending on care conditions and individual genetics.
Harlequin Rasbora feeds on: Pellets, Frozen food. Aim for a balanced diet with appropriate feeding frequency.
The price of Harlequin Rasbora varies significantly depending on morph, size, and lineage. Check our market price page for the latest pricing information.
Last updated: June 23, 2026